This invention relates generally to supplemental inflatable restraint (SIR) or airbag systems and more particularly to a cover assembly for concealing an SIR system in a vehicle passenger compartment.
U.S. Pat. No. 4,893,833 granted to Anthony J. DiSalvo and David J. Bauer Jan. 16, 1990 discloses a closure arrangement for an airbag deployment opening formed in an automotive instrument panel. The closure arrangement includes a closure panel positioned in the opening and hinged along one side, with a frangible lock on the opposite side that is fractured by pressure exerted by the deploying airbag. The closure panel comprises a core of lightweight rigid foam plastic bonded to a formed aluminum substrate and an outer vinyl skin. The closure panel is hinged along one edge by an extension strip of the aluminum substrate which is bolted to a structural support plate beneath the instrument panel.
There are several disadvantages to this single door closure arrangement. One disadvantage is that the closure panel is manufactured and installed as a separate unit which is not economical. The separate unit also has a visible outline that detracts from the appearance of the instrument panel.
U.S. Pat. No. 5,082,310 granted to David J. Bauer Jan. 21, 1992 discloses another arrangement for providing an airbag deployment opening in an automotive instrument panel involving an aluminum substrate. In this arrangement shown in FIGS. 9-11 of the patent, an aluminum substrate has a weakened bridging portion which is split apart to form contiguous doors. This dual door arrangement has the same drawbacks as the single door arrangement of U.S. Pat. No. 4,893,833.
U.S. Pat. No. 5,082,310 also discloses an invisible door arrangement in FIGS. 12-14 of the patent. This arrangement comprises a molded plastic substrate that also has weakened bridging portions that are split apart by the deploying airbag. This solves the appearance problem. However, the arrangement is still expensive to manufacture because the plastic substrate is made separately and attached to the adjacent substrate layer of the instrument panel before the foam layer is molded as shown in FIG. 13 of the patent. The specification states that the substrate may alternately be of integral construction. However, the specification and drawing do not show or describe details of any such integral construction.
U.S. Pat. No. 5,096,221 granted to Richard Combs and Scott Rafferty Mar. 17, 1992 discloses an automotive instrument panel having a separate tethered airbag door. The door has two substrates. The first metal substrate has construction holes for receiving fill nozzles on standard mold apparatus lids and holes to locate the substrate in the mold so as to form a sealed connection with respect to the outer cover and to define a space into which foam precursors are directed in a known manner. The second plastic substrate is fastened to the first substrate in a juxtaposed relationship so as to cover the holes. U.S. Pat. No. 5,161,819 granted to Richard D. Rhodes, Jr. Nov. 10, 1992 also discloses an airbag door with two substrates including a first metal substrate that has construction holes and locating holes and a second plastic substrate. While the arrangement of these two patents are improvements over the arrangement of U.S. Pat. No. 4,893,833, the arrangements have generally the same cost and appearance disadvantages.
U.S. Pat. No. 4,878,689 granted to Jurgen Mitzkus and Dieter Wiesner Nov. 7, 1989 discloses a steering wheel having a dual door arrangement for an airbag. Each airbag door has an aluminum substrate that is embedded in a foamed plastic. Each substrate has an arched outer edge region perforated by a plurality of holes arranged in two parallel rows so that the arched outer region acts as a hinge so that the door springs open easily.
U.S. Pat. No. 4,836,576 granted to Herbert Werner et al Jun. 6, 1989 discloses another steering wheel having a dual door arrangement. Each door has a polyamide reinforcing layer that is formed with apertures so that the reinforcing layer and the polyurethane foam layer of the covering will be held and will be anchored more effectively.